The present invention relates generally to fluid flow control systems and improved switching means for use therein, and specifically to air and vacuum switch controls for use in an air flow control system.
In this age of increasingly complex miniaturization, it is necessary to electrically connect and disconnect very small devices from printed circuit boards, etc. Where, in the past, a soldering iron was sufficient, it has been found that there is a need for a device which will not only melt the solder which makes the electrical connection but also to withdraw the excess solder from the area of the connection. Such a device, used both in the manufacture and repair of electrical devices, is the desoldering iron.
The desoldering iron has an air connection as well as the conventional soldering iron heating element. The air connection is connected to a very small aperture at the end of the desoldering iron such that once solder is melted, a vacuum applied to this air line will cause the melted solder to be sucked up through the aperture into an internal cavity in the desoldering device. In some instances, it is desirable to blow excess solder away from the connection and if an air pressure supply is connected to the air passageway, the force of air rushing out of the tip aperture serves to displace any dust, molten solder or the like from the vicinity.
It can be seen that it is desirable to be able to quickly change from a vacuum being applied to the desoldering device to a pressure being applied to the desoldering device. Additionally, it is desirable to be able to vary the pressure level applied to the desoldering device between some minimum and maximum amount. Furthermore, if a single pump is being utilized to supply both vacuum and pressure, it is desirable to operate the pump in as low a load condition as possible, i.e. when the air pressure outlet is connected to the desoldering device, the vacuum outlet of the pump is vented and vice versa. Additionally, when switching between vacuum and the air pressure position, it is desirable that both the pressure and vacuum be vented to prevent inadvertent loading of the pump.
Such a switch is disclosed and shown in U.S. Pat. No. 4,070,856 to Litt issued Jan. 31, 1978. The air flow switch disclosed in the Litt patent meets all of the above stated objects. However, it will be noted by reference to FIG. 2 and others that there are a number of separate parts which make up the switch requiring a rather expensive manufacture and assembly process.
Obviously, when the desoldering device is utilized in the vacuum mode, debris and dust are sucked into the vacuum pump causing increased wear thereon. Most systems require that an air filter be utilized between the air switch and the vacuum outlet of the pump in order to prevent excess pump wear. However, it has been found that in many instances, desoldering device operators will, when faced with a dirty filter, merely take out the filter and connect the switch directly to the pump outlet with a piece of tubing causing the above noted pump defects.